Open to anyone in the country, the DARPA Network challenge is designed to explore social networks and Internet communication. Finding balloons will require players to build and motivate nationwide networks of people to join the hunt.

The balloons, which will be visible only during daylight hours, are "moored, 8-foot, red, weather balloons at 10 fixed locations in the continental United States," DARPA explains on its Web site. The agency added that the balloons will visible and accessible from nearby roads.

The first person or team to send in the correct geographic coordinates for all ten balloons will pocket the $40,000 prize. Only those who have registered can submit locations and receive the prize, but they are free to divide the money however they'd like.

As of Friday, at least 2,000 people had registered for the contest and DARPA said the number continues to grow.

"We're learning a lot about how social networks form – how people band together to solve problems. But relatively less is known about how those networks mobilize rapidly and what happens when trust relationships are crucial," said Peter Lee, director of DARPA's Transformational Convergence Technology Office.

How Will Players Know Whom to Trust?

Until today, the contest has lived only online, where players have launched Facebook pages, Twitter accounts, wikis, Web sites, mobile device applications and more to promote their team and recruit members.

But now that the balloons are deployed, the real fun starts. Teams across the country are fielding and sharing messages, trying to separate accurate information from false leads.

"It's a race and money is involved. That injects a little twist. People now have an incentive to hold secrets," Lee said, adding that as players recruit other participants and solicit information they have to gauge whether or not they are legitimate.

Find the Red Balloon, Win Cash Prize

Since DARPA announced the project Oct. 29, Lee said a number of inventive approaches have popped up – from using different kinds of economic and charitable incentives to relying on computer security or data-mining technology to harnessing plain, old fun.

Jon Cannell, a 39-year-old small business owner in Port Charlotte, Fla., decided to join the contest early on. As an entrepreneur familiar with Web development, he figured he had as good a shot as anyone and launched a Web site, Facebook page and Twitter account to recruit members.

"I was excited by a challenge and thought maybe I could leverage some of my skills and learn new skills as they related to social media," he said.

After making his imprint online, he published a press release and asked friends and family to send messages about his project far and wide. To entice people to collaborate, he announced that the prize money would be split evenly among the people who submit winning coordinates.

Business School Tries to Active Alumni Network

Though his Facebook page counts just 20 people among its members, he believes the actual network of those aware of his team could be much larger and could still come through with valuable information starting Saturday.

"I'm not quite sure what to expect. It's basically a math problem – the more people in our network, the more the chance for success," he said.

Other teams are incentivizing participants with commitments to charity.

If it wins, Project Red Balloon, a balloon search team organized by graduate students and professors at Harvard Business School, promises to donate the $40k to AIDS research and awareness.

"We wanted to test the ability of 2,000 students and faculty on the Harvard Business School campus in Cambridge, Massachusetts to dig into their e-mail, their Facebook, and their Twitter networks to mobilize toward a common goal," MBA student Bradley Lautenbach said in an e-mail.

Through any means possible, he said their team is trying to engage the entire HBS community of current students and alumni across the country. He estimates that they've already reached 50,000 to 100,000 people in nearly every state in the continental U.S.

iPhone App Company Launches 'Army of Eyes'

"It's really a case of 'get out the eyes,'" he said. "We need as many people as possible, in as many places as possible, to be aware of what's happening on Saturday."

Hopefully, if someone sees a balloon they'll remember Project Red Balloon and report its location to them. Lautenbach said each person who submits a winning coordinate has the option to keep $1,000, but they hope each participant will choose to donate the money to charity.

For some tech professionals, the challenge is an opportunity to hone their skills and get their name out.

Mutual Mobile, an Austin, Tex,-based mobile applications development company, launched an iPhone application, "Army of Eyes," that makes it easy for iPhone users to snap a geo-coded picture of any red balloons they spot.

Mickey Ristroph, co-founder of the company, who previously competed in DARPA competitions, said, "This kind of challenge makes the most sense on mobile devices."

People will be on the road, or on foot, when they spot the balloons, he said. It's easier for potential participants to submit information immediately via smart phone than wait to go home and sit at their laptops.

Their incentive? To win $2,500 if they are the first to submit an accurate location. (Ristroph said Mutual Mobile won't keep any of the winnings.)

Having successfully developed and launched dozens of iPhone applications previously, he said his company was well-positioned to get "Army of Eyes" into the App store and into the public awareness. The application went live Wednesday and so far has been downloaded about 8,000 times.

Artist Will Create 30-Foot Balloon Cupcake if He Wins

For still other players, it's all about the fun.

Larry Moss, a professional artist who creates balloon sculptures, said he knew he had to join the competition the day it was announced.

Eighteen years ago he said he launched an online network for balloon artists in the Internet's earlier days. That network – balloonhq.com – is still thriving.

To celebrate the Internet's contribution to social networks, he's mobilizing his own, asking its more than 2,000 members to be on the lookout for the red balloons and spread the word about his project.

If his team wins, he said he will use the prize money to create a 30-foot-tall balloon cupcake, designed to fly with a pilot.

"You can do all the math and whatever tactics to play the game but when it comes down to it, I think people will respond to having fun," he said.

He also said that since the network will grow from an already established community, false information and distrust will likely not be significant issues.

"It's the birthday of the Internet – let's celebrate," he said. "What better way than with balloons and a cupcake."

-- This embed didnt make it to copy for story id = 9252014.
-- This embed didnt make it to copy for story id = 9252014.
-- This embed didnt make it to copy for story id = 9252014.
-- This embed didnt make it to copy for story id = 9252014.
-- This embed didnt make it to copy for story id = 9252014.